|
Hospitalizations and Deaths Rates of influenza-associated hospitalization are higher among young children than among older children when influenza viruses are in circulation and similar to rates for other groups considered at high risk for influenza-related complications (49,56-61), including persons aged >65 years (57,58). During 1979-2001, the estimated rate of influenza-associated hospitalizations in the United States among children aged <5 years was approximately 108 hospitalizations per 100,000 person-years (2). Recent population-based studies that have measured hospitalization rates for laboratory-confirmed influenza in young children have been consistent with studies that analyzed medical discharge data (29,32-34,60). Annual hospitalization rates for laboratory-confirmed influenza decrease with increasing age, ranging from 240-720 per 100,000 children aged <6 months to approximately 20 per 100,000 children aged 2-5 years (34). Estimated hospitalization rates for young children with high-risk medical conditions are approximately 250-500 per 100,000 children (53,55) (Table 2). Influenza-associated deaths are uncommon among children but represent a substantial proportion of vaccine-preventable deaths. An estimated annual average of 92 influenza-related deaths (0.4 deaths per 100,000 persons) occurred among children aged <5 years during the 1990s, compared with 32,651 deaths (98.3 per 100,000 persons) among adults aged >65 years (1). Of 153 laboratory-confirmed influenza-related pediatric deaths reported during the 2003-04 influenza season, 96 (63%) deaths were of children aged <5 years and 61 (40%) of children aged <2 years. Among the 149 children who died and for whom information on underlying health status was available, 100 (67%) did not have an underlying medical condition that was an indication for vaccination at that time (62). In California during the 2003-04 and 2004-05 influenza seasons, 51% of children with laboratory-confirmed influenza who died and 40% of those who required admission to an intensive care unit had no underlying medical conditions (63). These data indicate that although deaths are more common among children with risk factors for influenza complications, the majority of pediatric deaths occur among children of all age groups with no known high-risk conditions. The annual number of deaths among children reported to CDC for the past four influenza seasons has ranged from 44 during 2004-2005 to 67 during 2006-2007 (CDC, unpublished data, 2007). |